Jet engine throttle control



Jan. 5, 1954 w. B. MoRRls 2,664,762

JET ENGINE THROTTLE CONTROL Filed Allg. 5, 1951 2 Sheets-Sheet l Jlrl-5, 1954 w. B. MORRIS I 2,664,762

JET ENGINE THROTTLE CONTROL Filed Aug. 3, 1951 2 Sheets-Sheet 2 PatentedJan. 5., 1954 tijd JET ENGINE THROTTLE CONTROL Willis B. Morris,Hawthorne, Calif., assigner to Northrop Aircraft, Inc., Hawthorne,Calif., a. corporation of California Application August 3, 1951, SerialNo. 240,175

(Cl. i4-565) 2 Claims.

My invention relates to turbo-jet engine controls for airplanes, andmore particularly to the pilots throttle controls where the turbo-jetengines are equipped with afterburners.

The term afterburner is used herein as meaning any means for admittingfuel to a jet engine to be burned in the jet gas after it has passed theturbine wheel of the engine. Such additional fuel is ignited by the heatof the jet gas, and adds substantial thrust to the iet. However, thefuel economy is relatively poor, and afterburning is usually resorted toonly on takeoiis or to provide extra power in emergencies.

In the usual jet engine installation Where the engine is equipped withan afterburner, the throttle shaft of the engine controlling fueladmission thereto, has a minimum engine R. P. M. position, and a maximumR. P. M. position. It is required that fuel be admitted to theafterburner after the engine has reached a minimum of 90% R. P. M. It isusual for the throttle shaft to rotate beyond maximum R. P. M. position,to a position where fuel is also admitted to the afterburner.

A throttle arm is positioned for manual operation by the pilot of theairplane and is connected to rotate over a sector having positionscorresponding to the minimum R. P. M., maximum R. P. M., and afterburneron, positions, with a detent type of retard at the maximum R. P. M.position, so that the pilot will feel the retard but can overcome theretard to move the throttle arm freely thereafter into afterburningposition. lt has been found however, that such types of retardspositioned at the maximum R. P. M. position are often overridden in thenormal control of the jet engine R. P. M. by the pilot, and fuelaccidentally admitted to the afterburner when not desired.

Por example, the throttle arm can be moved by the pilot to maximum R. P.M. position before the engine actually reaches even 90% of maximum R. P.M. and if, under these circumstances, such as might occur' whenaccelerating after a balked landing, fuel were to be admitted to theafterburner, the result might well be disastrous because the afterburnerfuel would not burn properly.

lt is an object of the present invention to provide, in a jet enginethrottle control system in an airplane, means for preventing accidentaladmission of fuel to an afterburner in said engine.

lt is another object of the present invention to provide, in a jetengine throttle system, a firm indication to the pilot of the airplanethat 2 maximum R. P. M. position of the throttle has been reached.

It is still another object of the invention to provide means, in a jetengine throttle control, for imparting a forced time delay betweenmaximum R. P. M. position and the position at which fuel is admitted tothe afterburner. Such a time delay permits the engine to attain fullR..P. M. before the fuel is admitted to the afterburner.

-Other objects will become apparent as the description of the inventionprogresses.

Briefly the present invention in one form comn prises a throttle armoperable by the pilot of an airplane to control a turbo-jet engine inthe airplane between the minimum R. P. M. and the maximum R. P. M. ofthe engine, and movable beyond the maximum R. P. M. position to admitfuel to an afterburner in the engine. At the maximum R. P. M. positionthe throttle arm engages an inertia type governor, so that as thethrottle arm is moved by the pilot toward the afterburning position, theforce by which the throttle arm can be moved is increased over aremaining portion of the arc prior to reaching the position at which theafterburner fuel is turned on, and the pilot must, therefore, before theafterburner can be turned on, exert a steady and greatly increased forceto cause the arm to pass through the sector position over which thegovernor is engaged. Short of structural failure, it is impossible forthe pilot to rapidly push the throttle arm past maximum R. P. M.position, as the governor acts as a solid stop under these conditionsuntil the arm speed is reduced to a speed permitted by the governorunder the force applied. At any speed the inertia of the gov` ernormakes an unusually large force necessary for movement of the arm, ascompared to the force required to move the throttle arm between minimumand maximum R. P. M. positions. Thus a time factor is introduced betweenthe maximum R. P. M. position and the position Where fuel is admitted tothe afterburner, this time delay being sufficient for the engine toreach a safe R. P. M. before the afterburner is turned on.

My invention will be more fully understood by reference to the drawingsin which:

Figure l is a perspective View of a pilots throttle arm, along with adiagram showing con= nection to a turbo-jet engine driving an airplane.

Figures 2, 3 and 4 are side views of the governor shown in Figure l invarious operational positions.

Referring first to Figure l, an airplane i (only 3 partially shown) isprovided with a turbo-jet engine 2, the latter being mounted in theairplane l to provide an air inlet duct 3, and a tailpipe shroud t.Turno-jet engines, as at present used in airplanes, comprise acompressor portion 2a receiving air from inlet duct 3, a plurality ofcombustion chambers 2h in which fuel is burned in the air comingv fromcompressorsection 2c, and a turbine section 2c in which a turbine Wheel(not shown) is rotated by the heated compressed air.

the airplane as a jet through a tailpipe section 2d inside of thetailpipe shroud "ci to'provide-the' pro# pulsive thrust for theairplane.

As a substantial percentage or oxygen still remains in the turbine orthe engine, it has become customary, particularly in military airplanes,to releas'eiuel into the jet for burningzthis residual oxygen.

rihis may 'ce done for example, by the useiofaring type afterhurner 5disposed in the tailpipe seotionjust rearwardly ci the turbine wheel.Fuel releasedthrough fuel eed holes' inthe. afterburner ring iiimmediately ignitediby thev hot jet gas and burns, thereby providing asubstantial vadditional propulsive thrust for` the airplane.

However, as thefuel economy of such an'afterburner is very low,theraiteiourner' is only used when extraordinary thrust is required such'as for taire-offs, on short eldsiror, inthecase of mili.- taryairplanesy for military power in' einergencies, particularly incombat.

As the aiterburner thrust is highestwii-en the jetengine is running atfull R. P; lvl., it-.is customary for a throttle shaft i@ on thejetengine 2 to be made rotatable to control the fuel supply to. thecombustion chambers 'ib from.: zero` to maximum, andv then to hefurther.v rotatable to admitfuel `to the aiterhurner A. pilots throttle.arm lo is. positioned in the airplane to be manually moved over anarc inan arm housing i5, the arm 'labeingconnectedto the throttle shaft itthroughs. throttle arm pulley it, throttle cables il a throttle lever i3attached to the throttle shaft lil on the engine 2,

Grdinarily, a substantial angle of.' rotation of the throttle armifiiszused to move the throttle from ori or Zero engine R. P. M.position A, to engineR. P. M. position B, at'which point a spring detentdevice is normally installed, to he felt overridden by Vthe vpilotincase vhe desires to more the throttle arm lll beyond the maximum R. P.M. position Iinto afterburnerl on position C. This latter position is.reached by moving the throttle arm lf?!- over a smaller angle X to theend of the control sector, at which point fuel is admitted to theafterburner.

[is a .spring detentsuch 'as just described offer only a momentaryretard to the movement oi the throttle arm, the nature of a signal, itis readily possible ior the pilot to move the -arm iii past the detentinto afterburning position before realizing what he has done, and it isVpossible .for the aiterburner to be turned on before the engine hasreached the 99% maximum R. P. M. required for proper aiterhurneroperation. This is particularly apt to occur, and has occurred withdamage to the engine, wheniull acceleration is desired from idlingengine speed ior'exarnple.

To insure that proper engine speed is attained before the aiterhurner`can be turned on, the present invention utiliaesa governorwhich'prevents the arm lil from being moved rapidly Vover the angle Xbetween maximum R. P; M.. position The hot gases, after passing throughthe turbine section Ec are exhaustedvrearwardly orV hot gases passingf,through. l the" 4 B and afterburner on position C, and which forces thepilot to greatly increase the force necessary to move the throttle armI, thus providing a time delay during which time the engine speed cancatch up to throttle arm position.

One form this governor can Itake is shown in all the figures. A go ernorlever 2G is mounted on a pin 2l supported by a housing bracket 22 tohave an arm portion extending upwardly in the path of a governor block2e slidably attached to the side of the throttle arm ill. Block 213 isforeedtowardfthe axis of rotation oi arm l by block spring 25 and theblock is limited in travel byffhloclt pins 'attached to arm ill andoperating inslotsZi in block 2li. rihe end of arm portion liisprovidedwith acamming surface 28a sloping tovvardposition C.

Governor lever d extends below pin 2l in the formfof'a gear segment Sil.In engaging at all times a pinion 3l, mounted on a pinion shaft 3?.extended from bracket 22, governor lever 26 is urged `rearwardly byspring wound around pin El'andhaving one end engaging a tooth in gearsegment 3Q, the other end engaging a stop pin against which gear sectornormally rests; asbest shown in igure 2.

A. star wheel :is is attached to pinion 3l to he rotated with it, andthe points of star wheel llil are shaped to engage an ese-apement arefi! in a balanced wobble weight l2 free to rotate on a weight pin i3also supported by bracket 22.

The operation'oi the device at diierent positionsis'shown in Figures 2,3 and 4.

ln Fig re 2, arm block 2t is shown in its lower position contactingarmportion 23 of the governorv lever` 2li. rThis Contact is at iull R. P.M. position B. In order for the throttle arm l@ to. oe moved past thisposition, sufficient force must he used by the pilot to rotate governorlever' 2Q. which in turn rotates pinion 3l and attached star wheel fle.Star wheel di? cannot rotate without Wobbling wobble weight F22, whichdue to the inertia ofrepetitive direction change, prevents the pilotfrom moving the throttle it freely. between maximum RJ. P. M. position Bthe afterburner position C. The force must be continuously applied untila position is reached just prior to the aiterburncr on position C. Atthat point, Contact between arm block 2f? and arm523 of governor lever2l? is lost, as shown in Figure 3, and the governor lever 2d is free toreturn to its original position under the urge or" spring 33, leavingthe throttle arm iii iree to be moved slightly farther into afterburneron posil tion C.

When it is desired that the aiterburner be turned-oi and the throttlearm E4 returned to maximum R. P. M. position B, free movement of the armll is provided for, as arm block 2d on the return movement, hits theangular camming surface 23a on the end of the arm portion 23 of thelever Eil, andrises in slots 2l to pass over the arm portion 23. Armblock 2li then returns to its original position under the urge of clockspring 25.. The throttle arm lil is then hack in the engine R; P. M.range of the throttle arm ill.

It is to be noted that while the throttle arm ifi can be moved atvarious speeds through the range Where the force producing assembly isoperating, that Ythe' force required to move the arm increases as thearm speed is increased, and that this force must be continuously appliedover the entire range where the force producing assembly is inoperation.

Under .normal circumstances, when the pilot wishes to move the arm i4rapidly into the maximum R. P. M. position B, only a relatively lightforce is required. However, when Contact is made between the moving armblock 24 and the arm portion 23 of the governor lever, a solid stopeffect is produced for that force. -Continued progress of the throttlearm I4 past the maximum R. P. M. position requires the continuedapplication of a much higher force' by the pilot, a force that must bedeliberately and consciously exerted and maintained over a substantialarc of the throttle arm between maximum R. P. M. sector position andafterburner, and a time delay is important to the movement of thethrottle arm.

Thus the present invention makes it practically impossible for a pilotto accidentally move his throttle control arm into afterburningposition, and prevents such motion until the engine has had time toaccelerate to at least 90% full R. P. M.

While in order to comply with the statute, the invention has beendescribed in language more or less specific asv to structural features,it is to be understood that the invention is not limited to the specificfeatures shown, but that the means and construction herein disclosedcomprise the preferred form of putting the invention into effect, andthe invention is therefore claimed in any of its forms or modificationswithin the legitimate and valid scope of the appended claims.

What is claimed is:

1. A pilots throttle assembly for controlling a jet engine propelling anairplane, when said jet engine is equipped with an afterburner whichcomprises a throttle shaft on said engine rotatable from minimum tomaximum R. P. M. positions and beyond maximum R. P. M. position to admitfuel to said afterburner, a throttle arm shaft, a throttle arm mountedon said shaft and movable over a predetermined arc by the pilot of saidairplane, means connecting said arm shaft to rotate said throttle shaft,said arm arc including a minimum R. P. M. position adjacent one endthereof, an afterburner fuel admission position adjacent the other endthereof, and a maximum R. P. M. position intermediate said minimum R. P.M. position and said afterburner fuel admission position, said arm beingfree to move between said maximum and minimum R. P. M. positions at thewill of the pilot, a contact block slidably mounted on said arm, aspring urging said block to a lower position, a lever having one endthereof engageable with said contact block when said block is at saidlower position and at said maximum R. P. M. position to move said leveras said throttle arm is progressed over a substantial distance towardsaid afterburner fuel admission position, governor means connected to beactuated by movement of said lever, said block disengaging from saidlever as said afterburner fuel admission position is approached, meansfor returning said lever to its original position after blockdisengagement, and a camming surface on the end of said lever originallyengaged by said block, over which said block rides when said throttlearm is returned to maximum R. P. M. position.

2. Apparatus in accordance with claim 1 wherein said governor meansincludes a gear sector on the other end of said lever, a gear pinionengaged with said sector, a star wheel connected to said pinion, aweight pivoted adjacent said star wheel, said weight having anescapement area positioned to be engaged by said star wheel.

WILLIS B. MORRIS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,358,769 Mardis Nov. 16, 1920 1,473,971 Petersen Nov. 13,1923 1,998,362 Dodson Apr. 16, 1935 2,495,127 Oppel Jan. 17, 1950FOREIGN PATENTS Number Country Date 475,164 Great Britain Nov. 12, 1937626,297 Great Britain July 13, 1949

